Halohydantoin compounds have been widely used as a sensitizer for a photograph or the like or as a halogenating agent or an oxidizing agent for use in a process of producing a medicinal product, an agricultural chemical, a chemical compound, or the like. The halohydantoin compounds are considered as a promising compound because the halohydantoin compounds are stable and can be more economically produced by a known method. One of such halohydantoin compounds is 1,3-diiodo-5,5-dimethylhydantoin. As a method for producing 1,3-diiodo-5,5-dimethylhydantoin, for example, a method including the step of causing 5,5-dimethylhydantoin and iodine monochloride to react with each other in the presence of a base in a mixed solvent of an aqueous solution of a base and an organic solvent and a refining method have been disclosed (see, for example, Patent Literature 1 and Non-Patent Literature 1).
Non-Patent Literature 1 describes the following method: 5,5-dimethylhydantoin and iodine monochloride are reacted with each other with use of a sodium hydroxide aqueous solution and carbon tetrachloride. The resulting crystals are washed with water, and are further washed with anhydrous ethyl acetate. After that, the crystals are dried at 60° C. under a reduced pressure and thereby, 1,3-diiodo-5,5-dimethylhydantoin is refined. Non-Patent Literature 1 further states that the resulting 1,3-diiodo-5,5-dimethylhydantoin is a reagent so stable that it can be preserved without recrystallizing in a desiccator in a dark place.
Further, Patent Literature 1 gives the following description: First, 5,5-dimethylhydantoin and iodine monochloride are reacted with each other in a sodium hydroxide aqueous solution with use of N,N-dimethylformamide or an n-butyl acetate solvent. Next, the precipitated crystals as a result of the reaction are collected by filtration, and then, dried under a reduced pressure, thereby being refined.